The two heading rows were previously a little hard to pick out,
because they were alternately shaded like the commit rows.
R=adg
CC=golang-dev
https://golang.org/cl/5500074
* group builders in to columns by OS
* drop builder suffix (moved to hover title)
* cut all domain names from email (full name+email in hover title)
* make ok smaller
This should easily give us room for netbsd and plan9,
even on small laptop screens.
Running at http://build-rsc.golang.org/.
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5501064
